Quantitative differences in cell surface expression of class I MHC antigens on murine epidermal Langerhans cells

Epidermal Langerhans cells are derived from cells of bone marrow origin and, as the primary APC population in the skin, are responsible for initiation of many immune responses. Consequently, cell surface expression of MHC Ags by Langerhans cells is central to their function. Although murine Langerhans cells express class II MHC Ags at high levels, their level of expression of class I MHC has been controversial. In this study, cell surface expression of multiple individual class I MHC Ags on murine epidermal Langerhans cells was analyzed using quantitative immunofluorescence. It was found that Langerhans cells differentially express products of distinct class I genes. Langerhans cells expressed low cell surface amounts of H-2K and Qa-2, whereas expression of surface H-2D and H-2L by the same cells was high. Murine epidermal Langerhans cells therefore express low cell surface amounts of some but not all class I MHC Ags. Differential surface expression of products of distinct class I MHC genes by Langerhans cells may have a profound effect on cutaneous immune responses.